For some breathing disorders, the treatment may include delivery of a medicinal gas, sometimes at a relatively high flow rate. The provided gas is sometimes oxygen. Mask and tent oxygen therapy has been available for a long time. Conventional oxygen masks and appliances usually comprise tent-like structures that are usually strapped over the nose and mouth of a patient to create a fluidic pathway for gaseous medicaments or other gases.
Another current approach to gas delivery to a patient employs a small bore flexible tube with tubular open-ended nasal prongs and/or holes (jointly referred to as a cannula). Cannulae may be preferred over masks at times because it is often believed that cannulae are more comfortable than masks, they create a greater oxygen reservoir in the posterior pharynx and/or sinuses, and they create a better laminar flow and positive flow when respiratory effort is low.
Medicinal gasses delivered through oral and/or nasal cannulae have traditionally been limited, at least according to the literature, to a maximum of approximately 8 liters per minute (L/m). This was usually the result of the physical limitations of design, such as the physics of greater flow though a relatively small bore. Other limitations have included mucosal drying, gas delivery outside of a target area, delivery outside of target BTPS (Body Temperature and Pressure Saturated) values, discomfort and/or the like.
A high flow, warmed and humidified nasal oxygen delivery system that comfortably delivers nasal oxygen up to 40 L/m was recently introduced by Vapotherm, Inc., of Stevensville, Md.
While the medicinal gas is being delivered, it is often desired to obtain measurements of exhaled breath, in order to evaluate the patient's condition—whether his respiratory condition or a different medical condition.
An example of one of the many possible measurements of exhaled breath is Capnography, often defined as the measurement of the level of carbon dioxide (CO2). Since infrared light was found to be absorbed particularly well by CO2, capnographs usually measure infrared absorption in the breath gasses, which indicates the level of CO2 in these gasses. Other measurement technologies exist as well. The information obtained from a capnographic measurement is sometimes presented as a series of waveforms, representing the partial pressure of CO2 in the patient's exhaled breath as a function of time. Clinicians commonly use capnography in order to assess a patient's ventilatory status. Respiratory arrest and shunt may be speedily diagnosed, and a whole range of other respiratory problems and conditions may be determined by the capnographic measurement. Capnography is considered to be a prerequisite for safe intubation and general anesthesia, and for correct ventilation management.